The invention concerns a method for producing an electrical contact on a silicon carbide surface.
Electrical contacts on silicon carbide (SiC) are generally produced by applying a metal, such as for example platinum, tungsten, titanium, nickel, or chromium, directly onto a SiC surface. Both ohmic contacts and Schottky contacts on SiC are known.
From Appl. Phys. Lett., Vol. 65, No. 16, Oct. 17, 1994, pp. 2075-2077, a method is known for producing an ohmic contact on n-type cubic .beta.-SiC in which a 150-nm thick coating of titanium carbide (TiC) is deposited chemically from the gas phase (chemical vapor deposition=CVD) epitactically onto a (111) surface of the .beta.-SiC. The process gases used for this CVD process are TiCl.sub.4 and C.sub.2 H.sub.4.
One problem with these known methods for producing an electrical contact on a SiC surface is represented by the natural oxide formed on any exposed SiC surface in an oxygen atmosphere. In the case of ohmic contacts, this natural oxide coating increases the contact resistance. In the case of Schottky contacts, the oxide coating leads to a decrease in the contact barrier, and thus to higher leakage currents when a blocking voltage is applied. The natural oxide coating must therefore generally be removed, by sputtering or with hydrofluoric acid (HF), before application of the metal or the TiC.
From the publication Novel Refractory Semiconductors Symposium, Anaheim (US), April 21-23, 1987, Proceedings pp. 265-270, a method is known for producing an electrical contact on a SiC surface in which a carbon coating is created on a silicon carbide surface by evaporating off silicon atoms, said coating is treated with argon ions in order to remove silicon oxides, and the carbon coating is then converted, with titanium as the carbide-forming material, to titanium carbide. This method is comparatively complex due to the argon sputtering, since a separate vacuum process step is necessary.